Hemodialysis system having clamping mechanism for peristaltic pumping

ABSTRACT

A hemodialysis system including (i) an instrument; (ii) first and second peristaltic dialysate pumps operated by the instrument; (iii) a cassette including a rigid structure and first and second dialysate pumping tubes carried by the rigid structure; and (iv) a mechanism configured to initially allow the cassette to be accepted by the dialysis instrument after which the mechanism engages the first and second dialysate pumping tubes for operation with the first and second peristaltic dialysate pumps.

PRIORITY

This application claims priority to and the benefit as a continuation ofU.S. patent Ser. No. 12/257,014, now U.S. Pat. No. 8,114,276 entitled“Personal Hemodialysis System”, filed Oct. 23, 2008, which claimspriority to U.S. Provisional patent application No. 60/982,323, entitled“Personal Hemodialysis System”, filed Oct. 24, 2007, the contents ofeach of which are incorporated herein by reference and relied upon.

BACKGROUND

The present disclosure relates generally to medical treatments. Morespecifically, the present disclosure relates to medical fluidtreatments, such as the treatment of renal failure and fluid removal forcongestive heart failure.

Hemodialysis (“HD”) in general uses diffusion to remove waste productsfrom a patient's blood. A diffusive gradient that occurs across thesemi-permeable dialyzer between the blood and an electrolyte solutioncalled dialysate causes diffusion. Hemofiltration (“HF”) is analternative renal replacement therapy that relies on a convectivetransport of toxins from the patient's blood. This therapy isaccomplished by adding substitution or replacement fluid to theextracorporeal circuit during treatment (typically ten to ninety litersof such fluid). That substitution fluid and the fluid accumulated by thepatient in between treatments is ultrafiltered over the course of the HFtreatment, providing a convective transport mechanism that isparticularly beneficial in removing middle and large molecules (inhemodialysis there is a small amount of waste removed along with thefluid gained between dialysis sessions, however, the solute drag fromthe removal of that ultrafiltrate is not enough to provide convectiveclearance).

Hemodiafiltration (“HDF”) is a treatment modality that combinesconvective and diffusive clearances. HDF uses dialysate to flow througha dialyzer, similar to standard hemodialysis, providing diffusiveclearance. In addition, substitution solution is provided directly tothe extracorporeal circuit, providing convective clearance.

Home hemodialysis (“HHD”) is performed in the patient's home. Onedrawback of home hemodialysis has been the need for a dedicated watertreatment, which includes equipment, water connection and drainage.Installing and using those components is a difficult and cumbersome taskthat can require a patient's home to be modified. Nevertheless, thereare benefits to daily hemodialysis treatments versus bi- or tri-weeklyvisits to a treatment center. In particular, a patient receiving morefrequent treatments removes more toxins and waste products than apatient receiving less frequent but perhaps longer treatments.Accordingly, there is a need for an improved HHD system.

SUMMARY

The present disclosure provides a home hemodialysis (“HHD”) system. Inone embodiment, the home system includes a mobile cart and integral bagmanager. A latch is pulled out to unlock door of the system instrument.The door can be opened to expose a latch hook and peristaltic pumpheads.

The instrument accepts a disposable unit which in one embodiment isloaded from above and slid to the right. The disposable unit pivotstowards the machine interface, which allows peristaltic tube loops ofthe disposable unit to fit over peristaltic pump heads of theinstrument. Also, supply lines of the disposable unit are passed overindividual pinch valve plungers.

The pinch valve plungers pinch the supply tubes against a pinch valvestrike plate. The valve assembly is in one embodiment a motor-driven camoperated pinch valve subassembly. The motor in one embodiment is astepper motor.

The system in one embodiment includes a bellows or bladder thatcompresses a cassette against the instrument door using a pressure plateand gasket. These apparatuses are structured to accommodate an inlineinductive heater provided with the disposable cassette. The bellows isair actuated in one embodiment. The instrument includes a primary coilthat inductively heats conductive heating disks located within thecassette, which in turn heat fluid flowing through the cassette.

A multi-peristaltic pump race retracts and extends in one embodiment tofacilitate loading of the peristaltic tubes of the cassette onto theperistaltic pump heads. The race is then moved towards the tubes foroperation.

The system in one embodiment includes a manual blood pump operator,which allows the patient or caregiver to move the blood pump headmanually.

The system includes a bag management system having shelves that fold up,out of the way, and down, sequentially for placement of supply bags. Thesystem in one embodiment supports up to five, six liter solution bags.The bags can be dual chamber bags. The shelves in an embodiment areprovided with sensors that allow detection of whether the bags have been(i) loaded or not and (ii) opened or not for therapy. The sensors in oneembodiment are capacitive sensors placed on opposite ends of theshelves.

The disposable cassette in one embodiment connects fluidly to a heparinsyringe for the injection of heparin into the blood circuit. The syringefits into a luer connector assembly, which in turn is loaded into asyringe pump. The assembly is turned in the syringe pump to lock thesyringe in the syringe pump for treatment. The assembly accommodateslarge syringes, such as fifty to sixty milliliter syringes, which canlock directly into the syringe pump. In one embodiment, the heparin linepasses through the side of the cassette. Here, heparin can enter at theblood pump outlet just prior to the dialyzer inlet.

The system also includes a retractable saline bag support rod. Thesaline in one embodiment connects to the cassette near the heparin line.A saline valve is located on each side of the blood pump to control theflow of saline to same.

A dialyzer inlet pressure sensor interface in one embodiment doubles asa flow control valve. The cassette can also form an integral venus airseparation chamber.

Priming is performed in one embodiment via gravity. Gravity primes thevenous line, the arterial line and the air trap (drip chamber).

In another embodiment, priming is preformed via a combination of pumpingdialysate and a physiologically safe fluid, such as saline. Inparticular, a hemodialysis machine can include a blood circuit, adialysate circuit, a dialyzer placed in communication with the bloodcircuit and the dialysate circuit; and a priming sequence in whichdialysate is used to prime a first portion of the dialysate circuit anda physiologically compatible solution, other than dialysate, is used toprime a second portion of the dialysate circuit, the dialyzer and theblood circuit. The first portion of the dialysate circuit includes arecirculation loop primed by a dialysate supply pump in one embodiment.The second portion of the dialysate circuit can then be located at leastsubstantially between the recirculation loop and the dialyzer, and whichis primed by at least one of a blood pump and a downstream dialysatepump. In one embodiment, a volumetric balancing unit separates the firstand second portions of the dialysate circuit.

The cassette in one embodiment uses balance tubes to balance fresh andspend dialysate flow. The balance tubes have outlets at the top of thetubes when mounted for operation to allow air to leave the tubes. Thecassette also employs diaphragm valves that operate with a compliancechamber that seals against backpressure.

For instance, a hemodialysis machine can include a dialysis instrumenthaving at least one peristaltic pump actuator and first and secondpneumatic valve actuators. The instrument operates with a disposablecassette, the disposable cassette including a rigid portion, with atleast one peristaltic pump tube extending from the rigid portion foroperation with the at least one pump actuator. The rigid portion definesfirst and second valve chambers in operable connection with the firstand second valve actuators, respectively, the first and second valvechambers communicating fluidly with each other, at least the first valvechamber communicating fluidly with a compliance chamber, the compliancechamber absorbing energy from a pneumatic closing pressure applied toclose the first valve chamber, so as to tend to prevent the pneumaticclosing pressure from opening an existing closure of the second valvechamber.

The machine in one embodiment includes a vacuum applied to thecompliance chamber to absorb the energy from the pneumatic closingpressure applied to close the first valve chamber.

In the above example, a flexible membrane can be sealed to the rigidportion, the pneumatic closing pressure applied to the membrane to closethe first valve chamber. Here, the compliance chamber is formed in partvia a portion of the flexible membrane, wherein the flexible membraneportion is configured to absorb the energy from the pneumatic closingpressure. The cassette can alternatively include a flexible diaphragmlocated on an opposing side of the rigid portion from the flexiblemembrane, the compliance chamber formed in part via the flexiblediaphragm, the flexible diaphragm configured to absorb the energy fromthe pneumatic closing pressure.

The disposable cassette can have multiple compliance chambers operatingwith different sets of valve chambers. The compliance chamber aids bothupstream and downstream valves. The compliance chamber overcomes abackpressure applied by the closing of the second valve chamber to thefirst valve chamber, to allow the first valve chamber to close properly.

In another compliance chamber embodiment, the dialysis instrument has apump actuator and first and second valve actuators. A disposablecassette is operable with the dialysis instrument, the disposablecassette including a pump portion operable with the pump actuator, thefirst and second valve chambers communicating fluidly with each other,at least the first valve chamber communicating fluidly with a compliancechamber, the compliance chamber negating a first backpressure due to apneumatic closing pressure used to close the first valve chamber to helpto ensure the pneumatic pressure applied to the first valve chamber willclose the first valve chamber against a second backpressure from anexisting closure of the second valve chamber. Here, a pneumatic pressureapplied to the second valve chamber can be the same as the pneumaticpressure applied to the first valve chamber. The first backpressurewould exist around an outside of a port of the first valve chamber ifnot for the compliance chamber, the second backpressure existing insidethe port. As before, the compliance chamber is further configured totend to prevent the pneumatic pressure applied to the first valvechamber from opening the closed second valve chamber. And, the machinein one embodiment includes a vacuum applied to the compliance chamber toensure the pneumatic pressure applied to the first valve chamber willclose the first valve chamber.

In a further compliance chamber embodiment, the dialysis instrument hasa pump actuator and first and second valve actuators. The disposablecassette is operable with the dialysis instrument, the disposablecassette including a pump portion operable with the pump actuator, andfirst and second valve chambers operable with the first and second valveactuators, respectively, the cassette further including a compliancechamber in fluid communication with the first and second valve chambers,the compliance chamber defined at least in part by a rigid wall of thecassette and a diaphragm located on an opposing side of the rigid wallfrom the first and second valve chambers. The rigid wall in oneembodiment defines first and second apertures that allow the first andsecond valve chambers to communicate fluidly, respectively, with thecompliance chamber. The cassette can include a flexible membrane locatedon an opposing side of the cassette from the diaphragm, the membrane forclosing the first and second valve chambers. Again, the compliancechamber can aid at least one of: (i) maintenance of an existing closureof the second valve chamber when the first valve chamber is closed; and(ii) a proper closure of the first valve chamber at a time when thesecond valve chamber is already closed. In one embodiment, the aiding isprovided via a vacuum applied to the compliance chamber.

In still a further compliance chamber embodiment, a dialysis instrumenthas a pump actuator and first and second valve actuator. A disposablecassette is operable with the dialysis instrument, the disposablecassette including a pump portion operable with the pump actuator, andfirst and second valve chambers operable with the first and second valveactuators, respectively. A compliance chamber is placed in fluidcommunication with the first and second valve chambers, the compliancechamber defined by in part by a flexible membrane used to close at leastone of the first and second valve chambers, the valve chambers eachdefining an aperture for fluid communication with the compliancechamber. The disposable cassette can include a rigid wall, the first andsecond valves chambers extending from the rigid wall towards theflexible membrane, wherein the apertures of the first and second valvechambers are formed in the rigid wall, and wherein the rigid wall alsoforms a third, larger aperture to allow fluid flowing through the valvechamber apertures to communicate fluidly with the flexible membrane ofthe compliance chamber. Again, the compliance chamber aiding at leastone of: (i) maintenance of an existing closure of the second valvechamber when the first valve chamber is closed; and (ii) a properclosure of the first valve chamber at a time when the second valvechamber is already closed. Again, the aiding can be provided via avacuum applied to the compliance chamber.

It is therefore an advantage of the present disclosure to properly sealvalves in fluid communication with one another.

It is another advantage of the present disclosure to provide anefficient priming technique that combines the use of dialysate andanother physiologically safe fluid, such as saline.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of one embodiment of a personal homehemodialysis (“HHD”) system having a mobile cart and integral bagmanager.

FIG. 2 illustrates the system of the present disclosure, in which alatch is pulled out to unlock a door.

FIG. 3 illustrates the system of the present disclosure, in which a dooris opened exposing a latch hook and peristaltic pump heads.

FIG. 4 illustrates one embodiment of the system of the presentdisclosure, in which the door is hidden to more clearly show the doorlatch.

FIG. 5 illustrates one embodiment of the system of the presentdisclosure, in which a disposable unit is loaded from above and slid tothe right.

FIG. 6 illustrates one embodiment of the system of the presentdisclosure, in which the disposable unit is pivoted forward towards theinterface.

FIG. 7 illustrates one embodiment of the system of the presentdisclosure, in which the disposable unit pivots forward and the tubeloops fit over the peristaltic pump heads.

FIG. 8 illustrates one embodiment of the system of the presentdisclosure, in which the supply lines are placed in operablecommunication with individual pinch valve plungers.

FIG. 9 illustrates one embodiment of the system of the presentdisclosure, in which the supply lines are hidden to show pinch valveplungers.

FIG. 10 is rear view of one embodiment of the system of the presentdisclosure showing a pinch valve strike plate.

FIG. 11 is a perspective view of one embodiment of a cam operated pinchvalve subassembly operable with the system of the present disclosure.

FIG. 12 is another perspective view of the pinch valve subassembly ofFIG. 11.

FIG. 13 is a perspective view of the pinch valve subassembly of FIG. 11with its housing and motor hidden.

FIG. 14 illustrates a stepper motor operating with the pinch valvesubassembly of FIG. 11.

FIG. 15 illustrates blood lines operable with the system of FIG. 1.

FIG. 16 illustrates blood line clamps closed on the blood lines of FIG.15.

FIG. 17 illustrates one embodiment of a blood line clamp subassemblyoperable with the system of the present disclosure.

FIG. 18 illustrates one embodiment of a blood line clamp manualoverride.

FIG. 19 illustrates a user access to a manual override of the blood lineclamps.

FIG. 20 is a perspective exploded view of one embodiment of a doorshowing a pressure plate, gasket and bellows operable with the system ofthe present disclosure.

FIG. 21 illustrates the system with a door cover removed exposing tubesfor bellows.

FIG. 22 illustrates the system with the door hidden to better show aninline heating system.

FIG. 23 illustrates the system with the door and cassette hidden tobetter show a heater coil and wave heater disks.

FIG. 24 illustrates a front view of a retracted peristaltic pump race ofthe system of the present disclosure.

FIG. 25 illustrates a rear view of a retracted peristaltic pump race.

FIG. 26 illustrates a rear view of the peristaltic pump race extended.

FIG. 27 illustrates that an instrument housing supports the front of thepump race actuator shafts.

FIG. 28 illustrates one embodiment of a manual blood pump operation ofthe system of the present disclosure.

FIG. 29 illustrates a manual blood pump operation with the instrumentdoor closed and latched.

FIG. 30 illustrates one embodiment of a bag management system operablewith the HHD system having shelves folded up and ready for placement ofa first supply bag.

FIG. 31 illustrates a supply bag placed on a bottom shelf of the bagmanagement system.

FIG. 32 illustrates one embodiment in which the bag management systemcan hold up to five solution bags.

FIG. 33 illustrates the bag management system with all solution bagsconnected and bag peel seals broken.

FIG. 34 illustrates the bag management system with capacitive sensorsplaced on opposite ends of the shelves.

FIG. 35 illustrates one embodiment of a connection of disposable set toa heparin syringe.

FIG. 36 illustrates the syringe and luer connector assembly loaded intoa syringe pump.

FIG. 37 illustrates the connector of FIG. 36 rotated 45° to lock thesyringe into the syringe pump.

FIG. 38 illustrates that a large, e.g., 50/60 ml, syringe can lockdirectly into the syringe pump.

FIG. 39 illustrates one embodiment of a syringe pump mechanism operablewith the HHD system of the present disclosure.

FIG. 40 illustrates one embodiment of a viewing window for viewingheparin delivery.

FIG. 41 illustrates the heparin line passing through the side of thecassette and attaching to the backside of the instrument.

FIG. 42 illustrates that heparin enters at the blood pump outlet justbefore the dialyzer inlet.

FIG. 43 illustrates one embodiment of a saline bag support rod operablewith the HHD system of the present disclosure.

FIG. 44 illustrates the saline line connected to the cassette near theheparin line.

FIG. 45 illustrates a saline valve located on each side of the bloodpump.

FIG. 46 illustrates that the saline valve ports feed into each side ofthe blood pump.

FIG. 47 illustrates that a dialyzer inlet pressure sensor interface canserve additionally as a flow control valve.

FIG. 48 illustrates the venous and arterial lines are connected togetherto form a priming loop.

FIG. 49 illustrates one embodiment of a venous air separation chamberoperable with the system of the present disclosure.

FIGS. 50 and 51 illustrate one embodiment of a venous air separationchamber valve operable with the system of the present disclosure.

FIG. 52 is a fluid schematic illustrating one possible fluid flow regimefor the HHD system of the present disclosure.

FIGS. 53A and 53B illustrate one embodiment of a disposable set operablewith the system of the present disclosure.

FIG. 54 is a fluid schematic illustrating one embodiment for gravitypriming of the venous line, the arterial line and the air trap (dripchamber).

FIG. 55 is a fluid schematic illustrating one embodiment for pressurizedpriming of the dialyzer and purging of air from blood side circuit.

FIGS. 56 and 57 are fluid schematics illustrating one embodiment forpriming the dialysate circuit.

FIG. 58 is a section view of one embodiment for balance tubes havingoutlets at the tops of the tubes, the tubes operable with the HHD systemof the present disclosure.

FIG. 59 is a fluid schematic illustrating the HHD system of the presentdisclosure performing hemodialysis.

FIG. 60 is a fluid schematic illustrating the HHD system of the presentdisclosure performing pre-dilution hemofiltration.

FIG. 61 is a fluid schematic illustrating the HHD system of the presentdisclosure performing post-dilution hemofiltration.

FIG. 62 is a fluid schematic illustrating the HHD system of the presentdisclosure performing post-dilution hemodiafiltration.

FIG. 63 is a fluid schematic illustrating one embodiment for closing anarterial line clamp, opening a saline valve and infusing saline bolusduring therapy.

FIG. 64 is a fluid schematic illustrating one embodiment forrecirculating fresh dialysate in heater circuit and balance tubes toremove ultrafiltration (“UF”).

FIG. 65 is a fluid schematic illustrating one embodiment for closing avenous line clamp, opening a saline valve and rinsing back blood fromthe arterial line.

FIG. 66 is a fluid schematic illustrating one embodiment for closing anarterial line clamp, opening a saline valve and rinsing back blood fromthe venous line.

FIG. 67A is a perspective view of one embodiment of a disposableinterface subassembly operable with the HHD system of the presentdisclosure.

FIG. 67B is another view of the disposable interface subassembly of FIG.67A.

FIG. 67C is an exploded view of an internal module operable with thesubassembly of FIGS. 67A and 67B.

FIG. 68 is a perspective view illustrating springs at the four cornersof the subassembly of FIGS. 67A and 67B that retract the internal moduleof FIG. 67C.

FIG. 69 is a perspective view illustrating the backside of oneembodiment of a cassette interface faceplate operable with the HHDsystem of the present disclosure.

FIG. 70 is a perspective view illustrating the backside of oneembodiment of a membrane gasket operable with the HHD system of thepresent disclosure.

FIG. 71 is a perspective view of the internal instrument components fromthe backside of the hemodialysis system, showing that there is room foradditional, e.g., electrical, components.

FIG. 72 is a perspective view of one embodiment of the HHD systemoperating in conjunction with an online dialysate generation system.

FIG. 73A illustrates one embodiment of a diaphragm valve assembly havinga compliance chamber seal against backpressure, which is operable withthe HHD system of the present disclosure.

FIG. 73B illustrates one embodiment of a valve assembly havingcompliance chambers.

FIG. 74 is a perspective view of a disposable cassette having the valveassembly of FIGS. 73A and 73B.

FIG. 75 illustrates one embodiment of a peristaltic pump head sized tooperate with multiple supply lines for mixing different fluids of theHHD system of the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates one embodiment of asystem 10 sitting idle with its dust cover (not illustrated) removed. Ahandle 12 for a cart 14 is located in a lowered position to minimize thespace that system 10 consumes. Shelves 16 for the supply bags (shownbelow) are also shown in a lowered or “down” position, which minimizesthe height of system 10.

System 10 is programmed in an introductory state to instruct the user toopen a door 18 shown in FIG. 2. FIG. 2 illustrates a close-up view ofsystem 10 with a latch 34 pulled out to unlock door 18. Once door 18 isunlocked as seen in FIG. 3, it swings open, e.g., about forty-fivedegrees, and is held in the open position by a stop (not seen), so thata disposable set (shown below) can be loaded or unloaded.

FIG. 3 illustrates instrument 20 of system 10 with door 18 held in theopen position, exposing multiple peristaltic pump heads 22, a latch hook24, inductive heater coil 26 and a slotted area 28 for the blood lines(not illustrated) to run to and from the patient. Ultrasonic air bubbledetectors and optical blood/saline/air detectors are integrated into themolded slotted area 28 just above a cutout in the slot for the venousand arterial line clamps. The cutout located in slotted area 28accommodates the venous and the arterial line clamps. FIG. 16 shows thevenous and arterial line clamps 76 in the closed position, in which theclamps extend through a respective cutout. In an alternative embodiment,the inductive heater coil 26 is retracted into the system to facilitateloading.

In FIG. 4, door 18 is not shown for clarity to illustrate latch 34 andlatch hook 24, wherein latch 34 mechanically engages latch hook 24 tohold door 18 closed against the main portion of instrument 20. Onesuitable latch assembly is shown and described in FIGS. 11 and 13 ofU.S. Pat. No. 6,261,065, “System and Methods for Control of PumpsEmploying Electrical Field Sensing”, the pertinent portions of which areincorporated herein expressly by reference.

As seen in FIG. 5, once door 18 has been opened, system 10 prompts theuser to load the disposable set. A cassette 40 of the disposable set islowered into instrument 20 and moved to the right (with respect to theorientation of instrument 20 in FIG. 4). Cassette 40 is loaded startingat the upper left side of open door 18, so that the patient's bloodlines extending downwardly from cassette 40 do not interfere with theloading procedure. The patient's left hand can grasp a dialyzer 36connected to cassette 40, while the patient's right hand can grasp atubing bundle 38 formed by the supply and drain lines. Single handedloading is also possible, e.g., using right hand only grasp bundle 38 tomove both cassette 40 and dialyzer 36.

As seen in FIGS. 6 and 7, door 18 pivots cassette 40 forward towards acassette interface 50 of instrument 20 when an opening 42 in cassette 40is located directly over the inductive heater transformer coil 26. In analternative embodiment, transformer coil 26 is retracted to facilitateloading of cassette 40. In such case, coil 26 is then extended intooperating position after cassette 40 is loaded against interface 50. Abezel (not shown) provides locating stops for stopping cassette 40 inthe vertical and horizontal directions.

As cassette 40 mates with the cassette interface 50, the peristalticpump tubing loops 44 of cassette 40 slip over the vertically alignedpumping heads 22. A pump race 46 is retracted automatically upwardlywhen door 18 is opened to provide clearance between the pump heads 22and pump race 26 to facilitate the loading of pump tubing 44 andcassette 40.

FIG. 8 illustrates the supply lines 38 a to 38 e of bundle 38 (number ofsupply lines 38 can vary) passing over retracted pinch valves 48. System10 also retracts pinch valves 48 automatically when door 18 is opened tofacilitate the loading of bundle 38 and cassette 40 against interface 50of instrument 20. System 10 opens and closes pinch valves 48 in acontrolled manner, eliminating the need for manual clamps on supplylines 38 a to 38 e. FIG. 9 is shown with supply lines 38 removed to moreclearly illustrate pinch valve plungers 48.

FIG. 10 further illustrates pinch valve 48/supply line 38 interaction.Pinch valves 48 pinch supply lines 38 closed against a strike plate 52.In FIG. 10, four pinch valves 48 for supply lines 38 b to 38 e arepinching a respective supply line closed against strike plate 52, whilea fifth pinch valve 48 is retracted, allowing supply line 38 a to beopen.

FIGS. 11 and 12 illustrate a pinch valve subassembly 60, in which threeof the five plungers 48 are extended (closed state). Clamp heads 54 areconnected to a pinch valve body 62 of subassembly 60. FIG. 13 is shownwith body 62 removed to illustrate springs 56 that spring load pinchvalve plungers 48, e.g., so as to be normally closed. Springs 56 preloadpinch valve plungers 48, allowing for variations in the wall thicknessof supply tubes 38. FIG. 13 also illustrates that clamp heads 54 areformed with cam followers 58, which ride on associated cam lobes 62coupled to a camshaft 64 (FIGS. 11 and 14). A motor 66, e.g., a steppermotor, is coupled to a drive camshaft 64. FIG. 14 illustrates that inone embodiment, the individual cam lobes 62 each define aperturesconfigured fit onto a keyed portion 68 of shaft 64. FIG. 14 furtherillustrates the interaction of cam followers 58 and cam lobes 62.

FIG. 15 illustrates that when cassette 40 is loaded into instrument 20of system 10, blood lines 72 and 74 exit to the lower left of doorassembly 90 with venous and arterial line clamps 76 (FIG. 16) openinitially. FIG. 16 illustrates that venous and arterial line clamps 76pinch bloodlines 72 and 74 against housing portion 78 of instrument 20to close bloodlines 72 and 74. During normal operation, system 10operates clamps 76 independently as needed. FIG. 17 is shown withhousing portion 78 and door assembly 90 removed to more fully illustratevenous and arterial line clamp subassembly 70. A strike part of housingportion 78 seen in FIG. 16 is located between the venous and arteriallines 72 and 74 and pinches the lines together with the clamping levers76 when closed.

FIG. 18 illustrates the venous and arterial line clamp subassembly 70less a housing 77 shown in FIG. 17, in which clamps 76 are in the openposition. Subassembly 70 includes bellows 80 that hold clamps 76 openduring normal operation. Subassembly 70 also allows for an Allen wrench82 with a T-handle 84 to be used to operate a worm gear 86 that iscoupled operably to a cam 88, which cooperate to manually open both thevenous and arterial line clamps 76 if need be. In an alternativeembodiment, subassembly 70 includes dual worm gears and a split cam, sothat the venous and arterial line clamps 76 can be manually operatedindependently. FIG. 19 illustrates the placement of the T-handle Allenwrench 82 with respect to instrument 20 when the venous and arterialline clamps 76 are operated manually. In one embodiment, system 10causes an, e.g., red, flag (not illustrated) to protrude when the clamps76 have been opened manually. The flag retracts when the manual overrideis not engaged.

FIG. 20 illustrates an exploded view of the door assembly 90 taken frominside instrument 20. A pair of bellows or bladders 92 a and 92 b pushesa plate 94 having a gasket 96 to press the cassette 40 (not seen here)against the disposable interface 50 (not seen here). A space betweenbladders 92 a and 92 b is provided to accommodate the inductive heatercoil 26 extending from disposable interface 50. Alternatively,instrument 20 provides a single bellows (bladder) to press cassette 40against the disposable interface 50, which has an internal opening toaccommodate heater coil 26 extending from disposable interface 50.

In an alternate failsafe embodiment (not illustrated), the bellows 92 aand 92 b are replaced by a cavity with a diaphragm that is connectedsealably to front pressure plate 18. Springs are located between frontpressure plate 18 and the back wall of the cavity and press cassette 40against disposable interface 50, except when a vacuum is present withinthe cavity. In the alternative embodiment, system 10 can also introducepositive pressure into the cavity to increase the sealing force.

FIG. 21 illustrates system 10 with the door cover 98 (FIG. 20) removed.Pneumatic lines 102 a and 102 b to bellows 92 a and 92 b, respectively,are shown teed together before exiting door 18 through a hollow hinge104. A vertical metal bar 106 completes a circuit for the inductiveheater transformer primary coil 26 when the door 18 is closed againstinterface 50 of instrument 20. FIG. 22 is also shown with door 18removed to illustrate the inductive heating system including transformercoil 26 and a wave-shaped disk or disks 108 located in disposablecassette 40, which form a secondary coil that heats dialysis fluid dueto i²R losses. FIG. 23 removes cassette 40 to show inductive heater 100more clearly. Heater 100 transfers energy from the inductive coil of thetransformer 26 into wave washers 108 a and 108 b that are located withincassette 40. Washers 108 a and 108 b in turn heat dialysate as it flowsthrough cassette 40.

FIG. 24 illustrates the front of the instrument 20 with door assembly 90and device housing hidden to expose a mechanism 110 that extends andretracts triple peristaltic pump race 46. Mechanism 110 includes fouridler gears 112 that tie geared triple cams 114 together to move race 46to extend (towards tubing 44) and retract (from tubing 44) smoothly.Mechanism 110 is configured such that race 46 extends towards tubing 44only after door 18 is closed and latched to preclude the operator frombeing exposed to any moving components. The centers of pump heads 22 arealigned to provide clearance between the pump heads and triple race 46when the race is retracted.

FIG. 25 illustrates the backside of the retractable triple peristalticpump race 46 and mechanism 110 for moving race 46. Cams 114 are locatedat each end of race mechanism 110 and race 46. A middle cam 114 is alsoprovided. Each idler gear 112 (FIGS. 24 and 27) includes a shaft 113that transmits rotational motion from the idler gears to all three cams114 simultaneously. Cams 114 each include lobes 116 that rotatesimultaneously and in concert within large rounded end slots 118 tosimultaneously and evenly extend and retract race 46. Shafts 113 ofidler gears 112 (FIG. 24) maintain the horizontal orientation of theperistaltic pump race 46 as the race moves up and down.

FIG. 25 illustrates the cam lobes 116 rotated simultaneously and inconcert upwardly, pushing the pump race 46 away from gear motors 120that are coupled to pump heads 22. The open parts of the horizontallystabilizing idler guide slots are above the shafts 113 of idler gears.FIG. 26 illustrates the cam lobes 116 rotated simultaneously and inconcert downwardly, pushing pump race 46 towards the pump gear motors120 coupled to pump heads 22. The open parts of the horizontallystabilizing idler guide slots 122 are now below the shafts 113 of idlergears 112.

FIG. 27 illustrates molded support bosses 124 secured to instrument 20that support shafts 113 of the idler gears 112 and support the shafts115 of cams 114 on one end. A bar (not shown here but shown in FIG. 71),which mounts to bosses 124, supports the shafts 113 of gears 112 andshafts 115 of cams 114 on their other ends. A motor (not illustrated)drives cams 114, which operate the retractable pump race 46, and isattached to any of the shafts 115 of any of cams 114. Attaching themotor to the shaft of center cam 114 may be preferred so that clearancein the gear train is symmetric with respect to outer cams 114.

FIGS. 28 and 29 illustrate that system 10 includes a crank 130 that isconnected to the blood pump head 22 to operate the head manually. Manualreturn of the blood contained within the extracorporeal circuit isnecessary in the event of a failure of system 10 or after an extendedpower failure. It is typically necessary to manually operate the venousand arterial line clamps 76 (from a failed closed state) before beingable to return the blood in the extracorporeal circuit to the patient.FIG. 29 also illustrates that door 18 in one embodiment defines anopening or aperture 132 through which manual crank 130 for the bloodpump 22 can be inserted with the door closed. Crank 130 includes a largegripping handle 134 and crankshaft 136, which is sufficiently long toallow the user to easily turn blood pump head 22. In an alternateembodiment, manual crank 130 is built into the door assembly 90 and isaccessible to engage pump head 22 when door 18 is opened and hinged awayfrom machine interface 50.

As seen in FIG. 30, in one bag management embodiment, system 10 promptsthe user initially to fold up all of bag shelves 16 except for thebottom shelf 16. The user is then able to break a peel seal of a dualchamber bag (if used), place the first solution bag 140 on bottom shelf16 and connect the bag to the bottom supply line 38 e extending fromdisposable cassette 40, as shown in FIG. 31. When shelf sensors 138detect that the bag has been placed onto first shelf 16 and that thepeel seal 142 has been broken, system 10 prompts the user to place asecond bag 140 on the second lowest shelf 16, and so on. System 10continues to prompt the user to place solutions bags 140 onto shelves 16and connect the bags to supply lines 38 until all of shelves 16 arefilled, as shown in FIG. 32.

As shown in FIG. 32, a peel seal 142 of dual chamber bag 140 present onthe top shelf 16 is not broken, a condition which sensors 138 can sense,causing system 10 to instruct the user to break peel seal 142 beforecontinuing with treatment. One such sensor arrangement and peel sealopen check is described in U.S. patent application Ser. No. 11/773,742,entitled “Mobile Dialysis System Having Supply Container Detection”,filed Jul. 5, 2007, assigned to the assignee of the present disclosure,the pertinent portions of which are incorporated herein expressly byreference. FIG. 33 illustrates all solution bags 140 with peel seals 142broken, such that treatment can continue.

FIG. 34 illustrates one embodiment for the placement of the capacitivesensors 138 that detect the presence of the solution bags, whether peelseal is broken, and perhaps even whether the same solution is present ineach bag 140. Other sensors or combinations of sensors can be usedalternatively, including optical sensors, inductive sensors, bar codereaders, radio frequency identification (“RFID”) tags and cameras.

FIG. 35 illustrates a luer connection assembly 144, which is located onan end of a heparin line 146, which in turn is connected to disposablecassette 40. A heparin syringe 148 ranging in size from ten millilitersto sixty milliliters, can be connected to luer connection assembly 144of the disposable set and is inserted with the plunger 150 pointing downinto a syringe pump 152 as shown in as shown in FIG. 36. The luerconnection assembly 144 is then rotated to lock the syringe in place asshown in FIG. 37. Syringe 148, for sizes larger than 30 milliliters, isinserted with the plunger 150 pointing down into a syringe pump 152 asshown in as shown in FIG. 38. The integral grip 149 on the largerheparin syringes is rotated forty-five degrees to lock the syringe 148into the syringe pump 152 as shown in FIGS. 37 and 38 versus grip 149shown in FIG. 36.

Syringe pump 152 is shown in more detail in FIG. 39. Pump 152 includes astepper motor 154, gears 156, guide rails 158 and a concave push plate160 that self-centers on the end of the syringe plunger 150. Air exitssyringe 148 above the heparin and is purged during the priming of theextracorporeal circuit because syringe 148 is inverted for use. Steppermotor 154 increments 0.9 degrees per step in one implementation. Pump152 and assembly 144 are sized to accept nearly any size of syringe 148.The user inputs the syringe stroke length and syringe stroke volume intosystem 10. System 10 can thereafter determine the volume of heparin tobe delivered.

Smaller syringes 148 are visible through a window 162 in the side of thepump as shown in FIG. 40. Larger syringes housings are visible sincethey are not inserted into syringe pump 152 and remain outside ofinstrument 20 as illustrated in FIG. 38. Should a saline or dialysatebag leak, or be spilled, onto instrument 20, the liquid could flow intothe heparin pump and out the opening in side window 162 but would notflow inside the instrument, where the fluid could damage instrument 20.

FIGS. 41 and 42 illustrate that heparin line 146 passes through an airbubble detector 164 to cassette 40. System 10 introduces heparin intothe patient's blood stream at the outlet 166 of the blood pump justbefore the blood passes into the dialyzer. The internal volume of theheparin line is essentially that of a very small diameter tube ofminimum length. A diaphragm actuated pinch valve 165 (plunger only shownin FIG. 41), which does not add to the internal volume of the heparinline, can be provided to block the flow of heparin to cassette 40.

FIG. 43 illustrates a support rod 168 that collapses into instrument 20when not in use. Support rod 168 supports a saline bag 170 that is usedfor priming system 10 and rinsing blood back to the patient at the endof the therapy. Alternatively, rod 168 is detachable from instrument 20when not in use.

FIGS. 43 and 44 illustrate that saline line 172 enters instrument 20adjacent to the entry of heparin line 164 (see also FIG. 41). FIG. 45illustrates that two saline flow control valves 174 a and 174 b arelocated on each side of blood pump tubing loop 44. The center port fromeach of the valves feeds directly into blood flow into, or coming from,the blood pump as shown in FIG. 46. The third saline valve 174 c islocated on the backside of cassette 40 as seen in FIGS. 45 and 46 and ispositioned to put saline directly into a venous air separation (drip)chamber 176. The saline valve 174 a on the blood pump outlet, and thesaline valve 174 b leading to dialyzer 36, are opened sequentially togravity prime the arterial blood line and the venous drip chamber 176 asillustrated later in FIG. 54.

As seen in FIG. 47, a normally evacuated dialyzer inlet line pressuretransducer interface 178 is pressurized so that it operates as a flowcontrol valve, preventing saline from backflowing into the dialyzer orfilter 36. The gravity head from the saline bag causes saline to flowinto the blood circuit and into the reversed rotating pump inlet 180(the outlet under normal operating flow) when saline valve 174 a isopened. The reversed flow blood pump head 22 draws saline from thesaline bag and pumps it through reversed flow outlet 182 (the inletunder normal operating conditions) and down the arterial line 186.

As seen in FIG. 48, the venous line 184 and arterial line 186 areconnected in series during priming so that air is purged from both linesvia venous line drip chamber 176 shown in FIG. 49. Standard connections188 (FIG. 48) can be used to connect the venous line 184 and arterialline 186 in a closed loop. Gravity prevents air from being drawn fromthe saline bag as long as the bag contains saline. Saline flows slowlyinto the venous air separation chamber 176 in a “reverse” direction(from normal blood flow) during priming.

In FIG. 49, the inverted-U shaped venous air separation chamber 176 hasa vent port 190 located at its top, so that air can gather there and bevented to the drain. FIG. 50 shows a valve 196 located on the oppositeside of the cassette 40 from vent port 190, which is opened whenever airneeds to be vented from the chamber. A second vent valve 192 also shownin FIG. 50 can be placed optionally in series with first vent valve 196and operated sequentially so that predetermined volumetric increments ofair can be vented from system 10 to a controlled vent volume 194 shownin FIG. 51. As seen in FIG. 51, port 190 connected to the center of thecassette-based diaphragm valve 196 communicates with air separationchamber 176 so that the “dead” volume needed for these apparatuses isminimized. Valve 196 seals well against the pressure present in thevenous air separation chamber. Saline bags can be replaced during atherapy since they can be primed directly into the drip chamber 176using the third saline valve 174 c (FIG. 49).

FIG. 52 is a schematic of one embodiment of a fluid management systemassociated with the disposable set. In general, the fluid managementsystem includes a blood circuit 210 and a dialysate circuit 220. System10 operates the disposable set to provide the hemodialysis therapy. Set200 of FIGS. 53A and 53B illustrates an embodiment of a disposable set200 operable with system 10. Disposable set 200 includes cassette 40,filter 36, pump tubes 44, supply tubes 38, balance tubes 202, arterialline 184 and venous line 186, etc., discussed herein.

Once disposable set 200 has been loaded into the hemodialysis system 10,dialysate bags 140 have been connected, the saline bag 170 (FIG. 43) hasbeen connected and the heparin syringe 148 has been loaded, system 10primes itself automatically starting with the blood side circuit. Theheparin pump plunger 150 is moved forward until heparin is detected byheparin line air detector AD-HL shown in FIG. 52. Heparin valve V-H isthen closed. Next, saline is flowed from the saline bag 170 into theblood side circuit 210 as illustrated in FIG. 54, first through valveV-SA and then through valve V-SDC. A level sensor L-ATB in the AIR TRAPdrip chamber detects saline flow into the drip chamber 176 anddetermines when to close valves V-SA and V-SDC.

As shown in FIG. 55, the post pump blood valve V-PPB is then closed,V-SV is opened and PUMP-Blood pumps saline in a reverse flow direction.Pressure sensor P-VL and level sensor L-ATB are used to determine whento open air vent valves V-AVB-P and V-AVB-S. The blood pump pushes thesaline backwards down the arterial line and into the venous line. Whensaline reaches the venous air separator (drip chamber 176), the air willbe separated from the fluid and will be discharged into a drain line 206through vent valves V-AVB-P and V-AVB-S until the air separation chamber176 is flooded with saline.

Next, as seen in FIG. 55, saline is flowed up into the bottom ofdialyzer 36 and up through its hollow fibers. Valve V-PPB iscontrollably opened so that the air that exits the top of the dialyzer36 flows into the priming loop, becomes separated in air trap 176 anddischarged to drain 206. Saline is also flowed through pours of thefibers of dialyzer 36 to fill the housing of dialyzer 36. System 10monitors the pressure in the venous line using pressure sensor P-VL tomaintain the blood side circuit 210 at a controlled pressure duringpriming.

As seen in FIG. 56, spent dialysate pump, PUMP-DS and valves V-DS,V-B1-SI, V-B1-SO and V-DD vent air from the dialyzer housing to drain206. Valves V-DI-VEN, CK-VEN, V-DI-FIL, V-DI-PRE and CK-PRE are openedcontrollably to allow a predetermined volume of saline to be pushed intothe dialysate circuit 220, purging air from associated dialysate lines.A second saline bag 170 can be replaced during a therapy by selecting“replace saline bag”, causing the saline line to be primed automaticallyinto the air trap 176.

As shown in FIG. 56, dialysate valve V-DB1 that is associated with thedialysate bag on the top shelf is opened so that dialysate can flow intothe inlet of dialysate PUMP-DF. PUMP-DF pushes the dialysate through theinline fluid heater and into a dialysate side air trap 208. Dialysateflows out the bottom of the air trap 208, through valve V-FI and intobalance tube B2, through valve V-B2-FI, pushing fluid out the other sideof balance tube B2. The fluid exiting the other side of balance tube B2flows through valve V-B2-SO and into the dialysate recirculating circuit203 through valve V-DR. The recirculating circuit 223 tees into thesupply line circuit 205 at the inlet to PUMP-DF. Pump-DS is operating atthe same time drawing air, dialysate and/or saline from the blood sideof the dialyzer, though the dialysate side of the dialyzer, into theremainder of the dialysate circuit. PUMP-DS pushes the fluid throughvalve V-B1-SI and into balance tube B1, pushing fluid out the other sideof balance tube B1. The fluid exiting the other side of balance tube B1flows through valve V-B1-FO and valve V-DI-FIL into the dialysate sideof the dialyzer 36.

FIG. 57 is similar to FIG. 56 except the roles of balance tubes 202 B1and B2 are reversed. As fluid enters the dialysate circuit 220, thepressure in the circuit increases, forcing air to be discharged underpressure to drain line 206 through open vent valves V-AVD-P and V-AVD-S.

FIG. 58 illustrates balance tubes 202. Instrument 20 includes pairs ofoptical sensors (not shown) operable with balance tubes 202 to determinean end of travel of a separator 212 located within each balance tube202. The optical sensors in one embodiment are reflective, so that anemitter and receiver of each sensor can be on the same (e.g., non-door)side of balance tube 202. The sensors alternatively include emitters andreceivers located on opposite sides of balance tubes 202. Outlets 214 onboth ends of both balance tubes 202 are at the balance tube tops whenmounted for operation as shown if FIG. 58, so that air will pass throughthe balance tubes and not become trapped in the tubes as long as system10 is level. Mechanical stops 216 limit the movement of separators 212to that visible to the optical sensors.

FIG. 59 illustrates HHD system 10 performing hemodialysis. Here, freshdialysate is pushed from balance tubes 202 to dialyzer 36 via valveV-DI-FIL, while spent dialysate is removed from dialyzer 36 via valveV-DS to balance tubes 202.

FIG. 60 illustrates HHD system 10 performing pre-dilutionhemofiltration. Here, fresh dialysate is pushed from balance tubes 202to blood circuit 210 directly via valve V-DI-PRE, while spent dialysateis removed from dialyzer 36 via valve V-DS to balance tubes 202.

FIG. 61 illustrates HHD system 10 performing post-dilutionhemofiltration. Here, fresh dialysate is pushed from balance tubes 202to blood circuit 210 directly via valve V-DI-VEN, while spent dialysateis removed from dialyzer 36 via valve V-DS to balance tubes 202.

FIG. 62 illustrates HHD system 10 performing post-dilutionhemo-diafiltration. Here, fresh dialysate is pushed from balance tubes202 to (i) dialyzer 36 via valve V-DI-FIL and (ii) blood circuit 210directly via valve V-DI-VEN, while spent dialysate is removed fromdialyzer 36 via valve V-DS to balance tubes 202.

FIG. 63 illustrates one embodiment for closing arterial line clampV-ALC, opening a saline valve V-SA and infusing a saline bolus intoblood circuit 210 during therapy.

FIG. 64 illustrates one embodiment for recirculating fresh dialysatethrough Fluid Heater and recirculating circuit 223 and balance tubes B1and B2 to remove UF. In FIG. 64, pump-DF pumps fluid in a loop thatincludes Fluid Heater since valve V-DBY is open. Valve V-FI is closed sono fresh dialysate is delivered to balance chambers 202. Pump-DS pullsspent fluid from the dialyzer 36 through valve V-DS and pushes the spentfluid through valve V-B1-SI and into the right side of balance tube B1.Fresh fluid then flows from the left side of balance tube B1 throughvalves V-B1-FI and V-B2-FI and into the left side of balance tube B2.Spent fluid then flows out the right side of balance tube B2 throughvalves V-B2-SO and V-DD and into the drain line. In this manner, avolume of spent fluid is sent to drain 206 without a correspondingvolume of fresh fluid delivered from supply bags 140 to either balancechamber B1 or B2.

FIG. 65 illustrates one embodiment for closing venous line clamp V-VLC,opening a saline valve V-SA and rinsing back the arterial line 184.

FIG. 66 illustrates one embodiment for closing arterial line clampV-ALC, opening a saline valve V-SA and rinsing back the venous line 186.

FIGS. 67A to 67C illustrate a cassette interface assembly 250, whichhouses, among other items, cassette interface 50, door latch 24, heater26, a bellows bladder 252 and an internal module 260. Internal module260 is bounded by interface plate 50 and a back plate 254. Internalmodule 260 houses a plurality of gaskets 256, a pneumatic valve assembly258, a pinch valve assembly 262, and a plurality of manifold plates 264.

All or most all of the valves, pressure sensors, level sensors, etc.,can be removed without disassembly of subassembly 250. The inductiveheater mechanism 26 and bellows bladder 252 (different from bladder 92above) require removal of internal module 260. To this end, four screws266, each with a spring 268, fix a housing 270 of subassembly 250 tointernal module 260. Internal module 260 can be unbolted from screws266, so that springs 268 push internal module 260 forward and out of thehousing 270. Power and control connections (not shown) to subassembly250 are also disconnected to remove internal module 260 completely.

As seen additionally in FIGS. 68 to 70, four springs 268 on the backsideof subassembly 250 retract the internal interface module 260 whenbellows bladder 252 is not pressurized by pushing screens away fromhousing 270 and pulling interface module 260 along with the screws. Whenthe bellows bladder 252 is pressurized, internal module 260 is pushedforward and applies pressure to cassette 40, pushing the cassetteagainst a door gasket, which seals fluid pathways on both the front sideand the rear side of the cassette 40. The membrane gaskets 256 on theinternal module 260 mate up against the faceplate 50 of the interfacemodule 250. The faceplate 50 is configured so that it can support avacuum between the cassette sheeting and pressure sensors, liquid levelsensors, etc., bringing the sensors into intimate contact with thecassette sheeting and the fluid on the other side of the sheeting.System 10 is also configured to port a vacuum between the cassettesheeting and the thin sections of the membrane gasket 256 above thevalves. This vacuum can be used to detect holes, tears or slits in thecassette sheeting before, and during a therapy.

FIG. 71 is a view of the backside of system 10 with the cover removed.The open space houses interface assembly 250, hinged shelves 16,peristaltic pump motors 120 a pneumatic pump, a power supply, batteryand electronics that operate the system.

FIG. 72 illustrates system 10 operating alternatively with an onlinedialysate generation system 300. System 300 generates dialysate onlineor on-demand, eliminating bags 140, shelves 16 and multiple supply tubes38. A single supply tube 38 feeds from generation system 300 toinstrument 20. Water inlet line 302 and drain lines 304 lead to and fromgeneration system 300, respectively.

FIGS. 73A, 73B and 74 illustrate a cassette 40 diaphragm valve chamberconfiguration 280, which solves an inherent problem with diaphragmvalves have when attempting to seal against downstream pressure becausethe pressure that is trying to seal off the valve is acting on an areathat is just slightly larger than an area upon which the downstreampressure is acting. The difference between the two areas is the areadefined by the top of the “volcano”. Also, if the downstream fluidvolume is completely fixed when the diaphragm valve closes, furthermovement of the diaphragm is prevented after the initiation of the sealbecause of the incompressibility of the trapped fluid. The result isthat the downstream pressure equals the valve sealing pressure.Diaphragm valve configuration 280 provides a diaphragm valve that canseal against both upstream and downstream pressure via a connection oftwo diaphragm valve chambers 282 and 284 placed in series. Diaphragmvalve chambers 282 and 284 are connected fluidly via a compliancechamber 286, which allows sheeting seals 288 of the cassette sheeting toclose around respective volcano ports 290 of both valve chambers 282 and284.

Chamber configuration 280 in both FIGS. 73A and 73B includes a rigidmiddle or base wall 281 from which valve ports 290 and the valve chamberwalls extend upwardly. Wall 281 defines an aperture 283 for each valvechamber 282 and 284. Fluid communicates between valve chambers 282 and284 and compliance chamber 286 via apertures 283.

FIG. 73A shows a cross-section of two diaphragm valve chambers 282 and284 with an integral compliance chamber 286, wherein the diaphragms canreadily close seals 288 to ports 290. Here, a vacuum is applied to alower diaphragm 289 at the compliance chamber 286. Diaphragm 289 isflexible and has a relatively large cross-sectional area to absorb thekinetic energy created by a pneumatic valve actuator applying a positivepressure Pa, such that the positive sealing pressure applied to onevalve chamber 282 or 284 is much less likely to harm an existing seal ofa fluidly connected upstream or downstream valve chambers. The negativepressure pulls sheeting 288 down around ports 290 and allows valvechamber 282 or 284 to be sealed against the backpressure applied by itsown sealing pressure (around the outside of port 290) plus backpressurefrom a fluidly connected upstream or downstream valve chamber residingup through the center of port 290.

Compliance chamber 286 as seen in FIG. 73B is configured a little bitdifferently and uses a portion of the membrane or sheeting seals 288 ofvalve chambers 282 and 284 to provide a compliant material covering arelatively large cross-sectional area 292 of chamber 286. Here, a vacuumapplied to sheeting 288 at chamber 286 negates the positive pressure Pcapplied around the outside of ports 290 and expands the relatively largearea 292 of the valve seal sheeting, pulling sheeting 288 down aroundthe outside of port 290. The configuration of FIG. 73B is advantageousin one respect because positive and negative pressures are applied tothe same side of the cassette at chamber configuration 280, such thatassociated pneumatics can be located on a single side of the cassette.

By changing the pressure seen at compliance chamber 286 from a positivepressure when the valve chambers 282 and 284 are open to a negativevalue after the valve chambers results in that only the liquid sidecenter of the volcano port 290 is exposed to high positive pressure. Theliquid annular area of valve chambers 282 and 284 on the outside ofvolcano ports 290 sees the applied vacuum, which allows the air sealingpressure on the outside of the cassette to seal against backpressuresthat would have otherwise forced it open. This allows valve chambers 282and 284 to seals well in both upstream and downstream configurations.

In one example, suppose the total seal area of valve chambers 282 and284 is one square inch and that the sealing area at the top of volcanoport 290 is 0.1 square inch over the volcano. A positive ten psig airpressure would then apply an external force of 10 lbs to the entirevalve chamber 282 or 284. A backpressure on the annular fluid side ofthe associated port 290 from the applied ten psig pressure plus abackpressure the backpressure up through the center of port 290 from adownstream sealed valve would exert almost the same opposite “unsealing”force of ten pound (only difference would be the small annular area ofport 290 at the top, which is a function of the port wall thickness andthe diameter of the tube), resulting in a potentially leaky valvechamber 282 or 284. A higher positive pressure, e.g., twenty psig, couldbe applied to valve chamber 282 or 284 forcing sheeting 288 to seal toport 290 against the 10 psig backpressure, however, the noise generatedto create the twenty psig air pressure could objectionable to the user.There would also be no redundancy in the different valve pressures.

Back to back valve chambers 282 and 284 of FIGS. 73A and 73B, on theother hand, separated by an applied negative pressure, e.g., 5 psigvacuum, both seal independently well. The ten psig air pressure wouldstill apply 10 lbs external force to seal both valves 282 and 284,however, the 10 psig pressure at the center of the volcano port 290 andthe −5 psig pressure on the annular area around the volcano would applya total pressure of ten psig*0.1 sq in+(−5 psig)*0.9 sq in=−3.5 lbs. Thenet force to close the valve would be 13.5 lbs so that valve would sealvery well.

It may be possible to not use a separate vacuum and instead rely on theexpansion of the flexible part of the compliance chamber 286 to absorbenergy from the backpressure from one valve chamber 282 or 284 appliedto the other valve chamber 282 or 284. Here, apertures 283 allow thepressurized fluid inside chambers 282 and 284 and around ports 290 tocommunicate with fluid inside compliance chamber 286 and expanddiaphragm 289 or sheeting area 292, allowing the backpressure aroundports 290 to dissipate.

Valves V-DI-PRE, CK-PRE, V-DI-VEN and CK-VEN in FIG. 52 (and other flowschematics) and valve chambers 282 and 284 of valve configuration 280 ofcassette 40 shown in FIG. 74 are constructed as shown schematically inFIGS. 73A and 73B and can seal against higher pressure in eitherdirection. That is, not only does compliance chamber 286 serve to notdisrupt an existing upstream or downstream first valve chamber closurewhen a second valve chamber in fluid communication with the first valvechamber is opened, compliance chamber 286 also aids in the closure of afirst valve chamber when a second valve chamber in communication withthe first valve chamber (upstream or downstream) has been closedpreviously, which could otherwise create positive fluid pressure againstwhich the closure of the first valve chamber would have to fight.

FIG. 75 illustrates that system 10 in one embodiment includes a widepump head 22 that drives two dialysate pump segments 44 to mix twosolutions in a ratio that is approximately equal to the ratio of thetube inside diameters squared (mix ratio=(ID1/ID2)2), assuming the wallthicknesses of tubes 44 is the same. For a 1:1 mix ratio, consecutivesegments of tubing from the same roll of tubing can be taken to providesegments of the same wall thickness and good mixing accuracy. Mixingaccuracy is optimized because the inlet pressure on the supply lines iscontrolled within about four inches of water column by the bag manager,the tubing inner diameter is controlled during the manufacture of thedisposable set, the pump race diameters are the same and the pumpactuator rotational speed is the same for the parallel tubing segments.System 10 also ensures that an initial supply fluid temperature of eachof the different dialysis fluids in tubes 44 is within a few degrees ofeach other.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A hemodialysis system comprising: a dialysis instrument; first andsecond peristaltic dialysate pumps operated by the instrument; acassette including a rigid structure and first and second dialysatepumping tubes carried by the rigid structure; and a mechanism configuredto (i) initially allow the cassette to be accepted by the dialysisinstrument and (ii) thereafter move a member downwardly onto the firstand second dialysate pumping tubes for operation with the first andsecond peristaltic dialysate pumps.
 2. The hemodialysis system of claim1, wherein the member includes a cam race that engages the first andsecond dialysate pumping tubes.
 3. The hemodialysis system of claim 1,wherein the mechanism includes at least one cam configured to rotate tomove the member downwardly.
 4. The hemodialysis system of claim 3,wherein the mechanism includes at least one idler gear configured torotate the at least one cam.
 5. The hemodialysis system of claim 4,wherein the mechanism is configured to move the member away from thefirst and second peristaltic dialysate pumps after the door is latchedclosed.
 6. The hemodialysis system of claim 1, wherein the mechanism isconfigured to move the member away from the first and second peristalticdialysate pumps when a door for accepting the cassette is opened.
 7. Thehemodialysis system of claim 6, wherein the mechanism is configured tomove the member upwardly away from the first and second peristalticdialysate pumps when a door for accepting the cassette is opened.
 8. Thehemodialysis system of claim 1, which includes a motor, and wherein themechanism is driven by the motor.
 9. The hemodialysis system of claim 1,wherein the mechanism is configured to engage the first and seconddialysate pumping tubes at substantially the same time.
 10. Thehemodialysis system of claim 9, wherein the mechanism is cam-operated toengage the first and second dialysate pumping tubes at substantially thesame time.
 11. The hemodialysis system of claim 1, wherein the mechanismis configured to convert rotational motion to translational motion toengage the first and second dialysate pumping tubes.
 12. Thehemodialysis system of claim 11, wherein the mechanism is configured totranslate the member to engage the first and second dialysate pumpingtubes, the member including slots formed by walls that ride along camsrotated by the mechanism.
 13. A hemodialysis system comprising: adialysis instrument; first and second peristaltic dialysate pumpsoperated by the instrument; a cassette including a rigid structure andfirst and second dialysate pumping tubes carried by the rigid structure;and a mechanism configured to initially allow the cassette to be loadedonto a moveable platform of the dialysis instrument, after which themoveable platform and the mechanism are moved so that the mechanismengages the first and second dialysate pumping tubes for operation withthe first and second peristaltic dialysate pumps.
 14. The hemodialysissystem of claim 13, wherein the platform is a door connected moveably tothe instrument.
 15. The hemodialysis system of claim 13, wherein themechanism is configured to move a member and the first and seconddialysate pumping tubes towards each other to produce the operableengagement.
 16. The hemodialysis system of claim 13, wherein theinstrument provides a blood circuit, a dialysate circuit operated by thefirst and second peristaltic dialysate pumps, and a dialyzer placed incommunication with the blood circuit and the dialysate circuit, thesystem further configured to operate a priming sequence in which (i)dialysate is used to prime a first portion of the dialysate circuit and(ii) a physiologically compatible solution, other than dialysate, isused to prime a second portion of the dialysate circuit, the dialyzerand the blood circuit.
 17. The hemodialysis machine of claim 16, thefirst portion of the dialysate circuit including a recirculation loopprimed by at least one of the first and second peristaltic dialysatepumps.
 18. The hemodialysis machine of claim 17, the second portion ofthe dialysate circuit located at least substantially between therecirculation loop and the dialyzer.
 19. The hemodialysis machine ofclaim 18, the second portion of the dialysate circuit primed by at leastone of a blood pump and a downstream one of the peristaltic dialysatepumps.
 20. A hemodialysis system comprising: a dialysis instrument;first and second peristaltic dialysate pumps operated by the instrument;a cassette including a rigid structure and first and second dialysatepumping tubes carried by the rigid structure; and a mechanism configuredto (i) initially allow the cassette to be accepted by the dialysisinstrument, (ii) thereafter move a member into engagement with the firstand second dialysate pumping tubes for operation with the first andsecond peristaltic dialysate pumps, and (iii) when a door for acceptingthe cassette is opened, move the member away from the first and secondperistaltic dialysate pumps.